The present invention relates to a motor drive device and an integrated circuit device for motor driving, and to a technique effective if applied to a rotation control technique for a three-phase spindle motor of HDD (Hard Disk Driver) or the like.
As a system for driving a spindle motor of an HDD system, a soft switch system has been adopted which performs PWM corresponding to two phases upon energized-phase switching to thereby suppress a steep change in current. Although it is necessary to detect the position of a motor for the purpose of rotating the motor, it is known as a sensorless system that a de-energization period is provided after the energized-phase switching to detect a back electromotive force (BEMF) of the motor. Japanese Unexamined Patent Publication No. Hei 10(1998)-341588 (patent document 1) is known as one for detecting a current zero cross of each inductive load.